Iron by drip raised iron stores 20 times more than pills in a month. Did it also calm inflammation? Not convincingly

Iron deficiency is the most common nutritional deficiency in the world, and women of childbearing age carry much of it. Treatment comes two ways: tablets or capsules taken for months, or an intravenous infusion that delivers a large dose in minutes. The drip is known to refill iron faster. A question that gets less attention is whether either route changes markers of inflammation in the blood, since iron deficiency and low-grade inflammation tend to turn up together. A study published on 26 October in Nutrients by doctors at Dicle University in Diyarbakır, Türkiye, set out to look.

They followed premenopausal women aged 18 and over with iron deficiency, leaving out anyone pregnant or with an infection, autoimmune, kidney, liver or other chronic disease that could skew the results. The treating doctor chose the route. 72 women took a ferrous glycine sulfate capsule twice a day, 200 mg of elemental iron in all, on an empty stomach. 77 received ferric carboxymaltose by infusion, dosed for their weight and haemoglobin. Blood was taken before treatment and again on day 30. A further 76 women without iron deficiency gave one blood sample for comparison.

Before treatment, both iron-deficient groups had higher CRP (C-reactive protein) and ESR (sedimentation rate) than the healthy women: median CRP was 2.96 and 2.35 mg/L against 0.85 in controls. The groups were not evenly matched, though. Women chosen for the drip were more anaemic, with a median haemoglobin of 8.6 g/dL against 10.7 in the capsule group.

On repletion, the drip won clearly. Haemoglobin rose by a median 3.0 g/dL against 1.75 with capsules, and ferritin by 115.8 ng/mL against 5.6. On inflammation, the picture was thin. The median change in CRP was −0.22 mg/L with the drip and +0.07 with capsules, statistically different (p = 0.041) but tiny in absolute terms. When the researchers adjusted for age, starting haemoglobin and starting CRP, the day-30 difference was no longer significant. ESR on day 30 was 2 mm/h lower after the drip once adjusted, yet the change in ESR from the start was the same in both groups. Uric acid was higher after the drip in the raw numbers, but not after adjustment.

The authors are frank about why none of this shows the drip reduces inflammation. Women weren't randomised, and the sicker ones got the infusion. Every drip patient also received methylprednisolone, a steroid, together with paracetamol and an antihistamine half an hour before the infusion, and the capsule group didn't, so the study can't separate the iron from the steroid. Thirty days is short for capsules, which often take months to refill stores, and nobody counted how many capsules were actually taken. What the study does show is how much faster an infusion refills iron stores, with no infusion reactions recorded in this group.